Two-piece bladed diaphragm for an axial flow machine

ABSTRACT

A disc shaped bladed diaphragm structure for an axial flow turbine or compressor divided into two semicircular halves with radial grooves of mating cylindrical cross-sectional shape and having one or more cylindrical keying members disposed therein to provide a fluid seal thereacross; and a method of making a diaphragm with the seal structure described above.

O United States Patent [1 1 [111 3,788,767 Bednarczyk et al. Jan. 29, 1974 [54] TWO-PIECE BLADED DIAPHRAGM FOR 2,013,512 9/1935 Binnann 415/217 AN AXIAL FLOW MACHINE 2,217,500 10/1940 Spencer 415/217 2,247,387 7/1941 Johnson et a1... 415/217 [75] Inventors: Julian F. Bednarczyk, San Jose; 2,247,423 7/1941 Webster, Jr 415/217 James M. Gate, Saratoga, both of 2,661,147 12/1953 Anderson 415/217 Calif.

[73] Assignee: Westinghouse Electric Corporation, i y Husar Pittsburgh, Pa. Attorney, Agent, or Firm-A. T. Stratton et a1. [22] Filed: Dec. 1, 1971 21 Appl. No.: 203,817 [57] ABSTRACT A disc shaped bladed diaphragm structure for an axial 52 US. (:1. 415/217 turbine cmpressor divided into two semicir- 51 Int. Cl. F010 9/00 cular halves with radial grooves 0f mating cylindrical [58] Field of Search 415/216-218 Cross-Swim shape and having one more Cylindri- 7 cal keying members disposed therein to provide a fluid 56] References Cited seal thereacross; and a method of making a diaphragm with the seal structure described above. UNITED STATES PATENTS 1,641,665 9/1927 Devaud 415/217 9 Claims, 6 Drawing Figures g I60 Q\ 23d m 290 'T [5 u 310 35 I5 it- H G TWO-PIECE BLADED DIAPHRAGM FOR AN AXIAL FLOW MACHINE BACKGROUND OF THE INVENTION Turbines and compressors of the axial flow type are provided with stationary blades or vanes supported in an annular row by a disc or inner ring member and an outer ring member, the entire structure being known as a diaphragm. The diaphragm structure is employed in conjunction with the rotating blade of the machine to direct the fluid to the rotating blades as it progresses through the successive stages of the machine, as well known in the art.

Diaphragm structures of the type described above, and to which this invention pertains, are formed in two mating semi-circular halves for ease of assembly and service, and the machine casing structure is also formed in two mating halves of semi-circular crosssection. The casing halves are arranged to receive the associated diaphragm halves prior to installation of the rotor.

The diaphragm structure must be provided with a suitable annular seal structure surrounding the rotor shaft to minimize leakage of the fluid therepast to the next rotating blade row of the machine. This seal structure may be of any desirable type, for example,-it may be of the type shown in Gate et al. U.S. Pat. No. 3,309,095, issued Mar. 14, 1967 and assigned to the same assignee as this invention.

In addition to the above seal structure, the mating diaphragm halves must be provided with adequate sealing means at their diametric part line or joint to minimize fluid leakage therepast. When the diaphragm is initially formed as a circular unit and then cut into two halves, the material removed by the cutting tool (such as a saw kerf) forms a diametric gap or two opposed radial gaps that cannot be brought into mutual abutment, since each diaphragm half isof slightly less than 180 arcuate extent.

To overcome the gap produced by the removal of metal, it has been the practice to butter the and faces with weld deposited metal to the required annularly and then machine an abutting sealing surface to the degree required to restore each half to a full 180 arc.

SUMMARY OF THE INVENTION In accordance with the teachings of this invention, a diaphragm structure is provided having a disc shaped inner ring member and an outer ring shaped member arranged in concentric annularly spaced relation with each other and an annular row of stationary blades or vanes interposed therebetween and joined to the inner ring member and outer ring member in any suitable manner, for example, by welding. One manner of welding such a structure is generally disclosed in R. J. Ortolano et al. U.S. Pat. No. 3,313,520 issued Apr. 11, 1968 and assigned to the same assignee as the present invention. (In this patent, however, the diaphragm structure is initially formed of two diaphragm halves of larger arcuate extent than 180 and then they are machined to an arcuate extent of 180 to accurately mate with each other and form the two-piece divided diaphragm structure.)

The inner ring member and the outer ring member are initially provided with a pair of diametrically opposed, radially extending holes, such as by drilling, and

are prepositioned with these holes in axial alignment with each other during the assembly of the stationary blades thereto. After the blades are secured to the inner and outer ring members, the resulting structure is divided diametrically into two semi-circular halves along the axes of the radial holes, thereby splitting the holes into semi-circular grooves.

The resulting halves are thus provided with four pairs of mating concave cylindrical groove portions along their part lines. A cylindrical rod or keying member is inserted in each pair of mating grooves to form a high quality precision seal for preventing leakage of fluid through the diaphragm halves at the space or gap produced by the initial cutting of the one-piece diaphragm into the final two-piece diaphragm.

BRIEF DESCRIPTION OF THE DRAWINGS Reference may be had to the following drawings for a better understanding of the nature of the invention in which:

FIG. 1 is a cross-sectional view of an axial flow elastic fluid turbine having a bladed diaphragm structure formed in accordance with the invention;

'FIG. 2 is a radial sectional view taken on a larger side along line II-II in FIG. 1 and showing a portion of the lower half of the diaphragm;

FIG. 3 is a fragmentary sectional view taken on line IIIIII in FIG. 1 and showing the seal structure; and

FIGS. 4A, 4B, and 4C are fragmentary end views similar to FIG. 3, but showing several steps incurred in the method of making the diaphragm structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, in FIGS. 1 and 2, there is shown a portion of an axial flow, elastic fluid utilizing machine, for example, a steam turbine 10, comprising an outer tubular casing or housing 12 within which is disposed a rotor 13. The casing 12 is of generally circular cross-section and is divided into an upper semicircular half 12a and a lower semi-circular half 12b mating with each other. The upper and lower casing halves 12a and 12b may be joined together along a central horizontal plane P--P by suitable flanges l5, cooperatively associated with each other,'in any suitable manner, for example by bolts (not shown).

As best shown in FIG. 2, the turbine 10 is provided with a motive fluid expansion stage including a stationary bladed diaphragm structure 16 having an annular row of radially extending blades 17 peripherally attached thereto and disposed immediately upstream of a rotatable blade row 18, with respect to flow of elastic fluid S therethrough. The rotatable blade row 18 is carried by a rotor disc 19 forming a part of the rotor 13 and carried by a turbine shaft 20. The row of rotatable blades 18 extend radially outwardly from the disc 19 into the motive fluid stream S in a manner to be motivated thereby.

Although only one stage (16,18) has been shown and will be described in connection with the invention, a plurality of such stages may be employed in the turbine and each of such additional stages may be provided with the invention, if desired.

The diaphragm structure 16 serves to support the stationary blades 17 and to direct the motive fluid S to the rotating blades 18 in such a manner that the energy of the motive fluid is utilized in the rotating blades to drive the shaft of the rotor 13, as well known in the art. To minimize leakage of the motive fluid along the surface of the shaft 20 through the diaphragm structure 16, an annular seal structure 23 is employed. As illustrated, in the example shown, the seal structure 23 includes a labyrinthian seal ring divided into four arcuate segments 23a, 23b, 23c, and 23d movably carried by the diaphragm structure 16 and having a plurality of rows of ridges 24in closely spaced relation with the circumferential surface of the shaft 20. .l. M. Gate et al. U.S. Pat. No. 3,309,095 mentioned heretofore shows and describes more fully a preferred seal structure of this type.

The diaphragm structure 16, like the casing 12, is divided into upper and lower semi-circular halves 16a and 16b, respectively, with its lower half 16b disposed in the lower casing half 12b and its upper half 16a in the upper casing half 12a.

The upper and lower diaphragm halves 16a and 16b are substantially identical and are split into halves to permit assembly about the'turbine rotor shaft 20, as best shown in FIG. 1. However, in addition to the sealing requirement about the shaft 20 (met by the seal structure 23) it is highly desirable, if not absolutely essential, to prevent leakage of the motive fluid S through the diametric gap G between the upper and lower diaphragm halves 16a and 16b.

In accordance with the invention, the diaphragm structure 16 is preliminarily formed as an integral unitary structure and then cut along line parallel to the diameter to form the upper and lower halves 16a and 16b. During the cutting operation, some material is removed, leaving the gap G. For example, if the cutting is done by a metal cutting saw (not shown) the thickness of the saw kerf will determine the width of the gap G and the resulting diaphragm halves will have an individual arcuate extent of somewhat less than 180.

The diaphragm structure 16 comprises a disc or inner blade ring 25, an outer blade ring 26, an inner shroud ring 27 and an outer shroud ring 28 disposed concentrically, and with the stationary blades 17 extending radially between the inner and outer shroud rings 27 and 28, all of the above associated components being welded to each other. The outer ring 26 is divided into upper an lower semi-circular halves 26a and 26b and the lower diametric face portion of the upper half 26a is provided at both ends with a substantially semicylindrical groove 29a. In a similar manner, the upper diametric face portion of the lower half 26b is provided at both ends with a substantially semi-cylindrical groove 29b. The grooves 29a and 29b are disposed in registry with each other and are of the same radius. The groove 29b has a'mating cylindrical keying member 30 disposed therein with its outer convex surface in mating and sealing relation with the concave surface of the groove 29a, as best shown in FIGS. 1 and 3. The keying member 30 is of the same radius as' the mating grooves and extends radially substantially across the entire width of the outer ring, thereby acting to bridge the portion of gap G therein and forming a fluid restricting seal.

The inner blade ring 25 is also divided into upper and lower semi-circular halves 25a and 25b and the lower diametric face portion of the upper half 25a is provided at both ends with a substantially semi-cylindrical groove 31a. In a similar manner, the upper diametric face portion of the lower half 25b is provided at both ends with a substantially semi-cylindrical groove 31b. The two grooves 310 and 31b are disposed in registry with each other and are of the same radial extent. The groove 31b has a mating cylindrical keying member 33 disposed therein with its convex surface in sealing contact with the concave surface of the groove 31a. The keying member 33 and the mating grooves are of the same radial dimension and extend radially substantially across the entire width of the inner ring, thereby to bridge the portion of the gap G therein and form a fluid restricting seal thereacross.

The diaphragm halves are retained in the casing 12 at their outer blade ring halves by semi-circular recesses 36a and 36b. The lower recess 36b retains the lower outer ring half 26b while the upper recess 36a retains the upper outer ring half 26a.

To now summarize, the upper and lower halves 16a and 16b are sealed at their diametric part lines to restrict leakage of motive fluid through the gap G to the succeeding row of rotating blades 18. As seen in FIG. 1, the seal is effected by two keying rods or members 30 disposed on opposite ends of the outer blade ring structure 26 and two keying rods or members 33 disposed on opposite ends of the inner blade ring structure 23. Also, the keying rods 30 and 31 extend into endwise abutment with their associated outer and inner shroud rings 28 and 27, respectively.

The two pairs of mating grooves 290 and 29bin the outer ring are preferably provided by drilling a pair of radial holes 29 in diametrically opposed alignment with each other in the preliminary undivided outer blade ring 26, as indicated in FIG. 4A, wherein only a fragmentary portion of the undivided outer ring 26 has been shown. The portion shown in FIG. 4A is an end view of the outer ring corresponding to the right hand portion in FIG. 1 and FIG. 3.

Also the two pairs of mating grooves 310 and 31b in the inner ring are preferably provided by drilling a pair of radial holes in diametrically opposed alignment with each other in the preliminary undivided inner blade ring 25, (not shown) in the same manner as described and shown in connection with the outer blade ring 26.

The undivided inner and outer blade rings 25 and 26 are assembled with the stationary blades 17 and joined to each other, as by welding, and then divided, as initially described, along the plane PP to form the upper and lower diaphragm halves 16a and 16b. The resulting structure is thus provided in an extremely simple manner with the opposed mating grooves, for example as 'shown in 48, in connection with the divided outer ring structure 26a and 26b, which form perfect seats for the keying rods.

The keying rods may be retained in the lower diaphragm half 16b by any suitable means, such as by staking as indicated at 35 in FIG. 2. To facilitate securement of the keying rods to the lower diaphragm half 16b, the splitting operation is preferably conducted parallel to the axes of the holes 29, but slightly above the center C of the diaphragm 16 (as best seen in FIGS. 1 and 48) so that the grooves in the lower diaphragm half 16b are of slightly greater peripheral extent than the grooves in the upper diaphragm half 160.

With this arrangement, during assembly in the casing 12, the lower diaphragm half 16b may be initially rolled into place in the lower casing half 12b, below. the rotor shaft 13 and then the upper diaphragm half 16a may be superimposed on the lower diaphragm half above the rotor shaft 13 with its grooves 29a and 31a in perfect mating relation with the keying rods 30 and 33 in the lower diaphragm half 16b.

It will now be seen that the invention provides a di- We claim: 1. A disc shaped diaphragm structure for an axial flow machine,

said diaphragm structure being divided into at least two arcuate portions disposed with their radial surface portions in juxtaposed relation with each other,

said radial surface portions having mating concave cylindrical groove portions, and

a cylindrical keying member disposed in said mating grooves with its outer convex surface in sealing contact with the concave surfaces of said groove portions.

2. The structure recited in claim 1 in which the keying member has a radius of substantially the same size as the radius of said grooves.

3. The structure recited in claim 1 in which the mating concave grooves are in spaced relation with each other but are concentric with each other, and

the keying member extendsradially across the space to form the seal.

4. The structure recited in claim 1 in which the keying member is secured in one of the mating grooves and is held in sealing abutment with the other of the mating grooves.

5. A stationary diaphragm structure for an axial-flow machine, comprising an outer ring member, an inner ring member disposed in concentric radially inwardly spaced relation with said outer ring memher,

an annular array of vane members interposed between said outer and said inner ring members,

said outer and inner ring members being diametri' cally divided into two circular portions of slightly less arcuate extent than 180 and disposed with their radial surface portions in juxtaposed spaced relation with each other a distance equal to about one half of the increment between l and the actual arcuate extent of said. ring members,

said radial surface portions having mating concave cylindrical groove portions, and

a cylindrical keying member disposed in said mating grooves with its outer surface disposed in sealing abutment with the concave surfaces of said groove portions.

6. The structure recited in claim 5, wherein the keying member has a radial contour of substantially the same size as the radius of said grooves.

7. The structure recited in claim 6 in which the mating concave grooves are concentric with each other, and

the keying member is of circular cross-sectional shape with its convex surface in sealing contact with the concave surfaces of said grooves.

8. The structure recited in claim 6, wherein the keying member is secured in one of the mating grooves and is held. in separable sealing abutment with the other of said grooves.

9. The structure recited in claim 5, in which the radial surface portions of said inner ring members define two pairs of mating concave cylindrical groove portions,

the radial surface portions of said outer ring members define two pairs of mating concave cylindrical groove portions, and

a keying member as defined in claim 5 is disposed in each of said mating grooves. 

1. A disc shaped diaphragm structure for an axial flow machine, said diaphragm structure being divided into at least two arcuate portions disposed with their radial surface portions in juxtaposed relation with each other, said radial surface portions having mating concave cylindrical groove portions, and a cylindrical keying member disposed in said mating grooves with its outer convex surface in sealing contact with the concave surfaces of said groove portions.
 2. The structure recited in claim 1 in which the keying member has a radius of substantially the same size as the radius of said grooves.
 3. The strUcture recited in claim 1 in which the mating concave grooves are in spaced relation with each other but are concentric with each other, and the keying member extends radially across the space to form the seal.
 4. The structure recited in claim 1 in which the keying member is secured in one of the mating grooves and is held in sealing abutment with the other of the mating grooves.
 5. A stationary diaphragm structure for an axial-flow machine, comprising an outer ring member, an inner ring member disposed in concentric radially inwardly spaced relation with said outer ring member, an annular array of vane members interposed between said outer and said inner ring members, said outer and inner ring members being diametrically divided into two circular portions of slightly less arcuate extent than 180* and disposed with their radial surface portions in juxtaposed spaced relation with each other a distance equal to about one half of the increment between 180* and the actual arcuate extent of said ring members, said radial surface portions having mating concave cylindrical groove portions, and a cylindrical keying member disposed in said mating grooves with its outer surface disposed in sealing abutment with the concave surfaces of said groove portions.
 6. The structure recited in claim 5, wherein the keying member has a radial contour of substantially the same size as the radius of said grooves.
 7. The structure recited in claim 6 in which the mating concave grooves are concentric with each other, and the keying member is of circular cross-sectional shape with its convex surface in sealing contact with the concave surfaces of said grooves.
 8. The structure recited in claim 6, wherein the keying member is secured in one of the mating grooves and is held in separable sealing abutment with the other of said grooves.
 9. The structure recited in claim 5, in which the radial surface portions of said inner ring members define two pairs of mating concave cylindrical groove portions, the radial surface portions of said outer ring members define two pairs of mating concave cylindrical groove portions, and a keying member as defined in claim 5 is disposed in each of said mating grooves. 